1. Field of the Invention
The invention relates to a waterborne composition comprising styrene acrylic latex, vinylidene chloride-containing polymer latex and filler, which exhibits excellent sound damping property at both low and high frequencies.
2. Description of the Related Art
Various vibration and/or sound damping and corrosion resistant compositions for use on coating metal substrates are commercially available.
U.S. Pat. No. 4,952,610 discloses a sound damping composition comprising a urethane polymer, an oil-insoluble olefin polymer, and a filler. The composition can be used for damping noise in the frequency range of from about 50 Hz to about 5,000 Hz at a temperature of from about 150xc2x0 F. to about 350xc2x0 F.
U.S. Pat. No. 4,282,131 discloses a water based car underbody coating composition comprising a butadiene styrene latex, mica, and other additives. The composition is used for undercoating of vehicles to prevent corrosion and may exhibit, upon forming a film of high solid content, some sound or noise insulation.
U.S. Pat. No. 4,346,782 discloses a method of producing a vibration and sound damping coating that exhibits a sound damping property in a low frequency range of from about 20 to 1,000 Hz. The materials used in the method are plastisols based on polymers such as vinyl chloride polymers, acrylic polymers and liquid polyamide epoxide.
U.S. Pat. No. 6,130,284 discloses a vibration damping system comprising a substrate coated with a composition that exhibits sound damping property at a temperature of from about 0xc2x0 C. to about 60xc2x0 C. The composition comprises butyl rubber, a tackifying resin, a pigment and substantially spherical microspheres.
However, there is still a need for a high performance sound damping composition that exhibits excellent sound damping effect at a broader sound frequency range while retaining other desirable properties such as good chip resistance and abrasion resistance.
In one aspect, the invention provides a waterborne composition comprising:
a) from about 20 wt % to about 40 wt % of a styrene-acrylic latex having a glass transition temperature (Tg) of from about 0xc2x0 C. to about 30xc2x0 C.;
b) from about 5 wt % to about 20 wt % of a vinylidene chloride-containing polymer latex; and
c) from about 20 wt % to about 60 wt % of at least one filler, wherein said composition exhibits a composite loss factor of from about 0.02 to about 0.30 at a frequency of from about 100 Hz to about 1,400 Hz at a temperature of from about xe2x88x925xc2x0 C. to about 55xc2x0 C.
In another aspect, the invention provides an article comprising a substrate and a coating formed from the composition of the invention disposed on at least one surface of the substrate.
In yet another aspect, the invention provides a method of improving the sound damping of a substrate, comprising a step of applying the composition of the invention to at least one surface of the substrate to form a coating thereon. The coating may be air-dried at low temperature such as ambient temperature to up to 200xc2x0 F.
The composition of the invention can be formulated to exhibit excellent sound damping properties at low frequency, i.e., no greater than 1,000 Hz as well as at high frequency, i.e., from greater than 1,000 Hz to about 10,000 Hz at a temperature of from about xe2x88x925xc2x0 C. to about 55xc2x0 C.
The composition of the invention can also be formulated to be light weight, i.e. the specific gravity of the composition ranges from about 1.0 to about 1.5.
The composition of the invention can also be formulated to exhibit high chip resistance. In some embodiments the composition exhibits a chip resistance of rating 10.
The composition of the invention can also be formulated to exhibit abrasion resistance of at least 40 Kg.
The composition of the invention can also be formulated to exhibit very good adhesion when applied onto a substrate, such as cold rolled and galvanized steel, primed and painted steel, aluminum and painted aluminum, sheet molding compound (SMC), fiber glass and other plastics.
The composition of the invention can be used in a number of applications, including the transportation industry, the building industry, the aerospace industry and the appliance industry. The applications in the transportation industry generally include those parts of the vehicle which are subject to high structural noises (i.e., low frequency) and air borne noises (i.e., high frequency), which include the underbody parts, quarter panels, roofs, doors, interior, floor pan and wheel house.